This invention relates to a signal attenuator for use with a television set or an FM radio set.
Signal attenuators are widely employed being connected between a VHF or UHF antenna and a television receiver or an FM radio set in order to control the intensity of the incoming signal and to suppress external obstructive signals which interfere with the genuine signal from the antenna.
Hitherto, signal attenuators have constituted a .pi.-type, T-type or O-type attenuator circuit with a resistance material layer vapor-deposited on a ceramic substrate, or with chip resistors connected to electrodes of a ceramic substrate or an insulation substrate of a printed circuit. Such attenuators are liable to destruction or damage when hit by lightning directly or by a high voltage impulse wave caused by the lightning, through burning or the bursting of the chip resistors or connection parts between the element and the electrodes, thereby interrupting signal transmission, or at best, losing the designed attenuation characteristics such as frequency linearity of the attenuation and impedance.
Some trials have been made to add a discharge gap element comprising a pair of wires or plates supported to define a specified discharge gap therebetween. However, such addition of the discharge gap element usually adds undesirable inductance or stray capacitance to the delicate VHF or UHF attenuator, thereby lowering high frequency characteristic or causing impedance mis-matching to the relevant circuit.